1. Field of the Invention
The present invention relates to photography and, more particularly, to an accessory for a self-developing camera.
2. Description of the Prior Art
The present invention provides an accessory adapter which is attachable to a self-developing SX-70 Land Camera for providing a dark chamber or lighttight envelope on the exit side of a pair of pressure-applying rollers, into which a self-developing film unit of the transparency type may be advanced subsequent to the distribution of a fluid processing composition within the film unit. Such film units require a short imbibition period before being subjected to ambient illumination.
The SX-70 camera is designed primarily to expose and process integral self-developing film units or the type which provide a positive image reflection print. An example of this type of film unit may be found in U.S. Pat. No. 3,415,644 issued to E. H. Land on Dec. 10, 1968.
Subsequent to exposure, the reflection print film unit is advanced between a pair of pressure-applying rollers which rupture a pod or container on the film unit holding a fluid processing composition and distribute the fluid between a predetermined pair of layers of the film unit to initiate a development and diffusion transfer process.
Extending forwardly of the rollers is a camera housing section having a film exit slot in a bottom wall portion thereof. Intermediate the exit slot and the exit side of the rollers is a baffle or plate which is pivotally mounted on the bottom wall of the housing section, adjacent the exit slot, and is movable between a folded position wherein the plate is located in substantially parallel overlying relationship to the interior surface of the bottom wall and a normal extended position wherein the plate is inclined at approximately a 45 degree angle to the bottom wall and cooperates with side wall of the housing section and another camera housing section extending forwardly over the top of the rollers to form a lighttight chamber between the exit side of the rollers and the film exit slot. The length of the chamber is shorter than the length of the film unit.
In operation, the film unit advances through the pair or rollers and the leading edge of the film unit engages the erected baffle which deflects or gently bends the film unit from its normal path of travel and guides it to the film exit slot in the bottom wall where it emerges from the camera.
The baffle serves two functions. First, it provides a light free environment between the rollers and film exit slot so that light rays may not impinge a transparent exposure and viewing "window" of the film unit and be transmitted, within the confines of a transparent sheet forming the window, rearwardly to that portion of the film unit on the entrance side of the rollers that has not as yet been covered by the processing fluid. The processing fluid includes an opacification system which prevents ambient light from further exposing or fogging the photosensitive materials within the film unit. The second function of the baffle relates to improving the uniformity of fluid distribution within the film unit. It has been found that by inducing a gentle bend in the film unit as it emerges from the rollers, substantial improvement in reliably obtaining uniform and complete coverage of the photo-exposed area of the film unit is achieved.
For a more detailed explanation of the construction and operation of the baffle, reference may be had to U.S. Pat. No. 3,810,211.
When the trailing end of the film unit has passed through the rollers, approximately one half of the image area of the film unit extends outside of the camera beyond the film exit slot. The film unit may be removed immediately since it is protected from further exposure by the processing fluid.
The previously described camera structure extending forwardly of the pressure rollers is not suitable when transparency type self-developing film units are used in the SX-70 camera because the relatively short dark chamber between the rollers and film exit slot will not accommodate the entire film unit.
The prior art is replete with cameras that include full length dark chambers or light shields in front of the rollers for the purpose of receiving a self-developing film unit. Representative examples may be found in U.S. Pat. Nos. 3,650,188, 3,678,830, and 3,748,990. Also, see copending Ser. No. 466,371, filed on May 2, 1974, for an example of a camera having an extensible coiled light shield that covers over one side of a film unit for a limited period of time.
All of the prior art light shielding arrangements are: (1) intended to be built into the camera; and/or (2) do not completely light shield both sides of the film unit as is required when a transparency film unit is processed.